Based on real events, the story follows a father and son (Offerman and Tremblay) who identify as Sovereign Citizens, a group of anti-government extremists, as they venture across the country and find themselves in a standoff with a chief of police (Dennis Quaid) that sets off an intense manhunt with tragic consequences.

After Carlos, an impoverished teen from a fractured home, receives a desperate note from Sarah, a pen pal he lost touch with a year ago, he uses her letters to solve the mystery of her disappearance and crimes she may have been a part of.